Pyrolysis Behavior Research Articles

Effect of ethanolysis on the structure evolution, pyrolysis kinetics, and volatile products of waste poplar sawdust

Ethanolysis had been the promising approach for the deoxygenation of waste poplar sawdust (WPS), and its effect of structure variation and pyrolysis behaviors on the WPS was investigated in present research. The decreasing of C–O chemical bonds and the increasing of C content was typical phenomenon during the ethanolysis of WPS. The pyrolysis behaviors of sample were performed by thermogravimetric analyzer at three different heating rates. The pyrolysis kinetics and thermodynamics of WPS, residue230 (R230), and residue260 (R260) were well determined on the basic of three model-free iso-conversional methods. Average activation energy derived from the Kissinger-Akahira-Sunose (KAS) method of R260 displayed the high value (445.06 kJ/mol), followed by 224.88 kJ/mol for R230, then 200.68 kJ/mol for WPS. Thermodynamics data suggested that R260 required more total energy consumption for the breakage of chemical bonds. Additionally, pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) results showed that the highest relative content of volatile products compound derived from the flash pyrolysis of R230 and R260 was 47.12 % (d-Allose) and 38.69 % (Phenols), respectively, and RC value of arenes significantly increased to 15.82 % after ethanolysis. The findings would significantly contribute to the valuable utilization of waste biomass and its residues.

In situ construction of silicon-containing carbon layer by hyper silicone-branched structure endows epoxy/carbon fiber composites with high strength and ablation resistance

Epoxy/carbon fiber composites are widely used as structural materials in the aerospace field. Improving the ablation resistance of epoxy/carbon fiber composites is of great importance for the fabrication of highly integrated structural-thermal protection materials. In this study, a silicon-modified epoxy/carbon fiber composite was prepared by a hyperbranched structural design approach. By taking advantage of the excellent antioxidant properties of the silicone compounds generated by the pyrolysis of hyperbranched silicone structures, a dense char layer is rapidly constructed on the surface of composites. The characterization and thermal pyrolysis behavior of hyperbranched silicone-modified epoxy resins are analyzed. In the simulated aerodynamic environment of a high-speed vehicle (where the heat flow is 160 kW/m2), compared with epoxy/CF composites, the value of the mass loss rate of modified composites underwent a reduction exceeding 80%, accompanied by a 60.3 °C decrease in the maximum back-surface temperature. More significantly, the post-ablation mechanical properties were evaluated through a three-point bending test, revealing that the modified composites retained over 95% of their initial flexural strength and modulus after simulated pneumatic heating. This approach offers a new approach to manufacture structurally simple, integrated structure-thermal protection systems.

Initial pyrolysis of perhydroacenaphthene conformers: A multi-scale simulation and experimental analysis

The enduring quest for a fuel that embodies both high density and superior heat sink capacity has been a long-standing goal within the scientific community. Perhydroacenaphthene (PHAN) fuels, characterized by five-membered ring structure that enhances density, also serve as hydrogen donors to inhibit coking, showcasing significant potential in fuel applications. Given their "strain-free" cyclic configuration, PHAN fuels manifest diverse conformations like chair, boat, and twist, among others, each influencing fuel properties and subsequently affecting pyrolysis process and the utilization of heat sink. In this work, leveraging the five preferred PHAN conformers substantiated by experiments, we embarked on a comprehensive investigation into their microstructures, properties, pyrolysis behavior, and initial pyrolysis mechanisms combining with molecular simulation and experimental analysis. Among them, interaction region indicator (IRI) analysis was employed to elucidate the differences in density. Upon this foundation, taking trans-trans-trans and cis-cis-cis PHAN with minimum and maximum density as models, the effects of different conformations on the initial pyrolysis reaction were explored by micro-pyrolysis system attached to an online GC-MS/FID strategy. It was found that compared to the trans-trans-trans conformation, the cis-cis-cis conformation manifested superior initial pyrolysis activity and more substantial heat sink capacity. Moreover, upon delving into the reaction mechanism and microkinetic analysis, it became evident that the favored initial reaction type of PHAN pyrolysis was H-abstraction reaction, and cis-cis-cis PHAN presented a lower barrier and a faster reaction rate than trans-trans-trans. Additionally, in conjunction with the calculation of free energy barrier and reaction heat of numerous reactions, the kinetic and thermodynamic dominances for the initial pyrolysis pathways of trans-trans-trans and cis-cis-cis PHAN were identified. Finally, utilizing intermolecular interaction energy (ΔE), independent gradient model based on Hirshfeld partition (IGMH) and Xiamen energy decomposition analysis (XEDA), the microscale justification for cis-cis-cis PHAN conformation displaying superior initial pyrolysis activity was further unveiled. This endeavors pioneer innovative pathways for the directional development and application of PHAN conformers.

Effect of polyethylene terephthalate plastics on nitrogen, sulphur and chlorine contaminants via sludge pyrolysis and Pb/Cu adsorption properties of biochar

ABSTRACT Pyrolysis is an effective process for disposing of municipal sewage sludge (SS). Plastics can affect the SS pyrolysis behaviour and pyrolysis products due to their low ash and high hydrocarbon ratio. The secondary pollutants from the pyrolysis process may also be affected. Therefore, polyethylene terephthalate (PET), a typical plastic, was chosen to investigate the release characteristics of pollutants containing nitrogen, sulphur, and chlorine via SS pyrolysis, and the changes of biochar to adsorb two typical heavy metals, Pb and Cu. The pyrolysis of PET plastics facilitates the migration of N toward solid and liquid-phase products, S and Cl to the gas-phase products via pyrolysis. Oxygenated compounds of pyrolytic volatiles decreased from 38.18% to 28.43%, concurrently promoting the formation of phenolic compounds. The co-pyrolysis improved the quality of biochar and the ability to adsorb Pb and Cu. This systematic study can provide some support for the further improvement of SS pyrolysis technology, and will also be beneficial for subsequent applications.

Thermal safety effect of three alkaline impurities on 1, 2, 4-triazole

1,2,4-Triazole is a common intermediate used in the synthesis of pesticides and medicine, and has a very wide range of applications. As a kind of polynitrogen heterocycles, 1,2,4-triazole will release a lot of heat during thermal decomposition. If there is no comprehensive understanding of its pyrolysis behavior, there will be a very large thermal safety risk in the process involving 1,2,4-triazole in industrial production. At the same time, the instability of the substance may be affected by the presence of impurities, and the existing research on this aspect is quite scarce. Therefore, it is very necessary to study the effect of adding other substances on the thermal decomposition of 1,2, 4-triazole. The thermal decomposition characteristics and thermal runaway behavior of 1,2, 4-triazoles were revealed by thermodynamic experiments and various kinetic theoretical methods. According to the risk matrix, the thermal runaway danger level of 1,2, 4-triazole was determined to be level Ⅲ, which was an unacceptable risk. The results show that 1,2, 4-triazole has a huge heat release and the effect of thermal runaway is serious. In this study, three substances involved in the industrial production of fluconazole and flutriafol mixed with 1,2, 4-triazole were selected to explore their influence on the thermal decomposition of 1,2, 4-triazole under non-working conditions. DSC and ARC experiments consistently showed that these three impurities could reduce the reaction heat release of 1,2, 4-triazole to varying degrees, and confirmed that these three impurities could reduce the risk of thermal runaway of 1,2, 4-triazole to varying degrees. Among them, sodium hydride has the most outstanding performance, both in terms of reducing reaction heat release and reducing adiabatic temperature rise. The results can provide reference for loss control of 1,2,4-triazole in industrial applications.

Development of a pyrolysis reaction model for epoxy based flame retardant composites: Relationship between pyrolysis behavior and material composition

This paper presents a methodology to develop a pyrolysis reaction model that captures the flammability behavior of epoxy-based intumescent flame retardant coatings (EP/IFR) as a function of material composition. This approach adopted Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Microscale Combustion Calorimetry (MCC) experiments as well as the inverse modeling of the experimental results using ThermaKin2Ds and COMSOL Multiphysics modeling framework. The interactive reactions between EP and IFR were identified and quantified in the resulting lumped model, which is based on fitting of experimental data. It was found that the developed model was able to reproduce the TGA/DSC/MCC data within the prescribed criteria for EP/IFR blends with different material compositions. The model’s extrapolating capability was further validated through accurately predicting the experimental TGA data under different thermal conditions and for blends with different IFR ratios which were not used for model development. Additional TG-FTIR and XPS experiments were conducted to quantify the effect of IFR additive on the evolution of gaseous products and char formation. With a higher ratio of IFR, the amount of fuel dilution gases (i.e., CO2, NH3) was increased and the amount of combustible organic gaseous products was reduced. This work provides the core subset parameters for comprehensive pyrolysis modeling and enables the intelligent design of EP/IFR coatings with enhanced flame resistance.

Influence of different stalks on the metallization degree of FeCl3-derived magnetic biochar through pyrolysis behavior and compositional differences

To investigate the effect of stalk type on the metallization degrees in FeCl3-derived magnetic biochar (MBC), MBC was synthesized via an impregnation-pyrolysis method using six different stalks. The Fe0 content in MBC significantly influenced its magnetic properties and ostensibly governed its catalytic capabilities. Analysis of the interaction between stalks and FeCl3 revealed that the variation in metallization degrees, resulting from FeCl2 decomposition (6.1%) and stalk-mediated reduction (20.7%), was directly responsible for the observed differences in MBC metallization. The presence of oxygen-containing functional groups and fixed carbon appeared to promote metallization in MBC induced by reduction. A series of statistical analyses indicated that the cellulose, lignin, and hemicellulose content of the stalks were key factors contributing to differences in MBC metallization degrees. Further exploration revealed that hemicellulose and cellulose were more effective than lignin in enhancing metallization through FeCl2 decomposition and reduction. Constructing stalk models demonstrated that the variance in the content of these three biomass components across the six stalk types could lead to differences in the metallization degree attributable to reduction and FeCl2 decomposition, thereby affecting the overall metallization degree of MBC. A prediction model for MBC metallization degree was developed based on these findings. Moreover, the elevated Si content in some stalks facilitated the formation of Fe2(SiO4), which subsequently impeded the reduction process. This study provides a theoretical foundation for the informed selection of stalk feedstocks in the production of FeCl3-derived MBC.

Effects of Na-salt solutions on the biomass pyrolysis and CO2-assisted gasification behavior

This study aims to explore the effects of different Na-salt solutions on the behavior of biomass pyrolysis and gasification. The same molar number of Na was introduced via the impregnation method. The distinction was that pine wood impregnated with neutral NaCl and Na2SO4 solutions was the Na in physical adsorption form, whereas the alkaline Na2CO3, CH3COONa, and NaOH solutions resulted in both carboxylate form and physical adsorption form. Thermogravimetric analysis results showed that impregnating alkaline Na solution was more potent than the neutral Na solution in reducing the thermal stability of pine wood structures. Results of pyrolysis and CO2-assisted gasification indicated that samples impregnated with the alkaline Na solutions obtained lower CO and higher CO2 evolution than that from the neutral Na solution during pyrolysis. The Na in carboxylate form was more difficult to volatilize, and formed more Na-containing active catalytic structures, resulting in biochar that provided higher reactivity in gasification. However, different Na solutions on the biochar's gasification reactivity showed the order of NaCl-loaded sample < CH3COONa-loaded sample ∼ NaOH-loaded sample < Na2SO4-loaded sample < Na2CO3-loaded sample. This can be attributed to the combined effects of Na-containing active catalytic structures, along with the active surface salt complex formed by molten Na species and biochar. As for the overall energy efficiency of pine wood impregnated with different Na solutions, gasification of Na2CO3-loaded sample provided the highest maximum overall energy efficiency (49.2 %). The results presented here provide useful insights for practical application of using syngas for electricity generation.

Role of sodium sulfate in electrical conductivity and structure of lignin-derived carbons

Lignin is a promising renewable alternative to fossil fuels for producing carbon materials such as carbon fibers, activated carbons, or carbon black. Despite extensive research, lignin-derived carbon materials show limited graphitization relative to comparable petroleum-derived carbons. Further, lignin-derived carbons show high variation in graphitization and electrical conductivity depending on the source of the lignin. Herein, nine lignins, derived from various feedstocks and isolation procedures, are pyrolyzed to produce biochar at 1100∘C. These lignins have a range of chemical compositions, carbon structures, and particle sizes. As a result, the pyrolysis behavior of these lignins varies, with powdered, clumped powder, and “foam” biochar morphologies resulting from finely powdered lignin. The produced biochars vary widely in both electrical conductivity, from 0.19 to 19 S/cm, and in-plane graphitic crystallite size, from 3.4 to 41.2Å. A significant decrease in electrical conductivity is identified when Na2SO4 is removed from lignin, accompanied by an increase in graphitic crystallite size. Based on this finding, a quadratic relationship between biochar graphitic crystallite aspect ratio and electrical conductivity is proposed that builds on established quasi-percolation models for biochar electrical conductivity.

Co-pyrolysis of poly (lactic acid) and sugar cane bagasse: Kinetic and thermodynamic studies

For the purpose of investigating the effect of biomass on pyrolysis degradation of plastic wastes, poly (lactic acid) (PLA) has thus been attempted in present work to study the influence of sugar cane bagasse (SCB) on its pyrolysis behaviors and kinetic paramerizations. PLA/SCB samples after prepared by using a suspension blending method have been co-pyrolyzed in nitrogen by non-isothermal thermogravimetric analysis. After adding SCB biomass, the initial pyrolysis degradation temperatures and melting point of PLA are found to have declined substantially. Using pyrolysis results, activation energies of Ea are isoconversionally calculated by applying differential Friedman, integral Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, Starink and Vyazovkin-Dollimore methods, resulting in 113.7 ∼ 141.7, 101.3 ∼ 140.4 and 79.8 ∼ 210.1 kJ/mol for the PLA blends with 10, 20 and 30 mass% of SCB, respectively. Two approaches based on the Friedman differential equation along with integral methods are attempted for determining pre-exponential factor lnA and pyrolysis reaction model f(α). With these modeled results, the experimental curves are matched successfully. Moreover, thermodynamic parameters including ΔH, ΔG, and ΔS values were calculated for the entire pyrolysis process of three blends. The findings acquired from present study are of significance for advancing the design of any relevant pyrolysis reactor for PLA/biomass wastes.

Comprehensive study of alkali lignin pyrolysis catalyzed by composite metal-modified molecular sieves for the preparation of hydrocarbon liquid fuels

Catalytic lignin pyrolysis for hydrocarbon liquid fuel production offers a viable alternative to fossil fuels. This study investigated the effects of transition metal (Fe, Co, Ni, Cu) modified composite molecular sieve catalysts on the pyrolysis product distribution and behavior of alkali lignin (AL). AL pyrolysis achieved the highest liquid product yield of 24.50 % at 600 °C, with high temperatures favoring hydrocarbon product formation. Volatile gaseous products from AL pyrolysis included H2, CO, CO2, phenolic compounds, heteroatomic compounds, and hydrocarbons. Molecular sieve catalyst additions were all favorable to the increase in hydrocarbon content. Compared with ZSM-5 and SBA-15, catalysts processed through acid etching and metal modification exhibited optimized pore structure, acid site distribution, and catalytic performance. Metal-modified composite molecular sieve catalysts (FeZS, CoZS, NiZS, and CuZS) generated more liquid products and promoted hydrocarbon formation. Notably, Cu-modified ZS catalysts exhibited superior acid site distribution and specific surface area, considerably reducing oxygenated compounds in the products. A higher catalyst-to-feedstock ratio increased the number of catalytically active sites, facilitating the cracking and deoxygenation of oxygenated components and generating more hydrocarbon products. The highest hydrocarbon yield for AL with a catalyst-to-biomass ratio of 10:1 under CuZS was 92.25 %, with 66.07 % being monocyclic aromatic hydrocarbons (MAHs) and 61.72 % benzene, toluene, ethylbenzene, and xylenes (BTEX). Additionally, kinetic and thermodynamic analyses revealed a substantial decrease in the average activation energy (Eα) of AL and a reduction in entropy value with the CuZS catalyst, indicating enhanced pyrolytic reactivity of AL. Therefore, the proposed method is highly effective for producing highly selective hydrocarbons through catalytic pyrolysis of AL.

2D Modeling and Simulation of Pyrolysis of a Thermally Thick Biomass Particle

ABSTRACT A transient 2D kinetic-heat transfer model incorporating primary and secondary reactions is proposed to investigate the effect of reactor temperature and particle length/diameter (L/D) ratio on the pyrolysis behavior and validate it with the experimental results. The RMS error between the experimental and the model predictions are found to be 0.36–1.89% for 2D model and 13.00–13.11% for 1D model at reactor temperatures 723–798 K and L/D of 1.0. This uncderscores the necessity for the use of the 2D model in place of the 1D model, particularly at the lower L/D ratio. Temporal propagation of temperature and mass fractional residue profiles at different locations of the pyrolyzing casuarina (Casuarina equisetifolia) biomass particle is analyzed. At a high L/D (~6), two symmetric hot spots are found to appear at two axial end faces, which gradually merge to form a dumbbell-shaped hot spot near the central core. For a low L/D (~1), a symmetrical, concentric, elliptical, shell-shaped hot spot appears at a short distance from the outer surface, which quickly propagates toward the center, eventually merging into a sphere at the particle center. It is estimated that for a 0.0254 m diameter particle at the reactor temperature of 673 K, the optimal residence time is 10 min for L/D = 1, while it is 17 min for L/D = 2.

Investigation on pyrolysis characteristics and kinetics of sewage sludge with different heat-mass transfer rates

The pyrolysis process of sewage sludge (SS) in fluidized bed has the characteristics of high speed heat-mass transfer rate, which challenges the reliability of thermal analysis methods. In this study, TGA and fast-reaction thermogravimetric analysis (FR-TGA) were used to investigate the pyrolysis characteristics of SS. The apparent kinetic parameters of pyrolysis at constant heating rate (β) and excellent heat-mass transfer rate were obtained, respectively. Resuls shows that, the pyrolysis of SS under both conditions showed multi-step reaction characteristics. The apparent activation energy (Eα) of pyrolysis of SS determined by FR-TGA was significantly lower than that determined by TGA. With the increase in temperature of the FR-TGA reactor, E decreased further. The excellent heat-mass transfer rate could improve the reactivity during SS pyrolysis. In addition, FR-TGA experiments showed that moisture could promote the pyrolysis of organic components in SS and further reduce Eα. Based on these conclusions, a kinetic model of SS pyrolysis under excellent heat-mass transfer rate was established. This study can serve as a reference for predicting the pyrolysis behavior of SS in a fluidized bed reactor.

Wastewater phosphorus enriched algae as a sustainable flame retardant in polylactide

Revolutionizing our polymer industry for adaption to a sustainable carbon circular economy has become one of today's most demanding challenges. Exploiting renewable resources to replace fossil-fuel—based plastics with biopolymers such as poly(lactic acid) (PLA) is inevitable while using waste streams as a raw material resource at least is promising. When it comes to using PLA as technical polymer, its high flammability must be addressed by flame retardants compatible with the thermoplastic processing of PLA and its compostability. This study proposes microalgae enriched with phosphorus from wastewater (P-Algae) as an elegant way towards a kind of sustainable organophosphorus flame retardant. The concept is demonstrated by investigating the processing, pyrolysis, flammability, and fire behavior of PLA/P-Algae, while varying the P-Algae content and comparing P-Algae with four alternative bio-fillers (phosphorylated lignin, biochar, thermally treated sewage sludge, and metal phytate) with different P-contents as meaningful benchmarks.

Hydrochar from winemaking industry wastes as solid biofuel: A thermal and kinetic analysis of pyrolysis and combustion

Pyrolysis and combustion behavior of the hydrochar (HY) from co-hydrothermal carbonization (co-HTC) of vine pruning (VP) and exhausted grape marc (EGM) by using vinasse as wet catalytic vector was investigated through thermogravimetric analysis (TGA). For both raw- and co-HTC biomass, different iso-conversional methods were used for kinetic analysis, and the thermodynamic parameters were determined. Overall, even if HY exhibited a lower activation energy compared to EGM and VP during both pyrolysis and combustion, HTC has positive effects on the hydrochar’s structure, which achieved a more thermodynamically stable, structurally ordered, and energetically favorable state. The obtained kinetic and thermodynamic parameters would contribute to the development of biomass thermochemical conversion technologies and the application of hydrochar-based energy systems.

Thermogravimetric analysis on two Bambusa texlitis wastes slow pyrolysis behaviors and kinetics using isoconversional and parallel-reactions models

In this work, the pyrolysis behaviors and kinetics of two bamboo (Bambusa texlitis) wastes were investigated via thermogravimetric analysis. The weight loss behaviors of pyrolysis were studied by curvature of the conversion (α) curves. The curvature of α can depict the characteristic temperatures of pseudo component (hemicellulose, cellulose and lignin) pyrolysis. Model-free model was applied to estimate the apparent activation energies of the pure components for comparison with other kinetic models. Three parallel reaction (TPR) and parallel finite number first-order reaction (FNFOR) models were used for kinetic studies. The first-order TPR model underestimates the apparent activation energies of pseudo components. The nth-order TPR model underestimates the apparent activation energy of lignin and obtains characteristic temperatures that are inconsistent with those of pure lignin. The parallel FNFOR model is more reliable for simulating the kinetics of lignocellulosic biomass pyrolysis. The apparent activation energies of pseudo components depend on the variety of lignocellulosic biomass.

Pyrolysis behavior of densified refuse-derived fuels (d-RDFs) via TGA: Investigating the impact of densification degree on thermal kinetics and thermodynamics

The conversion of municipal solid waste (MSW) into its energy-rich fraction, known as refuse derived fuel (RDF), addresses both MSW management and energy demand. RDF comprises a diverse blend of various non-hazardous waste streams, making it challenging to predict physical properties and chemical compositions. However, densification can help overcome these challenges. This work aims to explore the effect of densification degree on kinetic and thermodynamic parameters during the degradation of densified refuse-derived fuels (d-RDFs) in inert atmosphere. Herein, three d-RDFs samples obtained with varying degree of densification and die temperatures ranging from 55 °C to 118 °C, as well as a mixed fines (MF) sample produced during the pelletization process, were analyzed. Pyrolysis potential of d-RDFs and MF were determined using thermogravimetric analysis in the temperature range from 30 to 800 °C, at multiple heating rates of 5, 10, and 20 K min−1. The effect of the degree of densification on physical characteristics, and kinetic and thermodynamic parameters of d-RDF was investigated. Apparent activation energy (Eα) was estimated employing Friedman (FR), Kissinger-Akahera-Sunnose (KAS), and Flynn-Wall-Ozawa (FWO) methods. Derived Eα values were used to determine the pre-exponential factor (Aα) using the Kissinger method. Experimental results revealed that the durability of d-RDFs increased from 79.26 % to 98.73 % as the densification degree increased from II to IX. Furthermore, the Eα values exhibited a decreasing trend in the first peaks of the DTG profiles, while an opposite trend was observed in the second peaks of DTG curves. However, with an increase in the degree of densification, the mean values of Eα decreased by 5–10 % for all methods. The Aα values, assessed using the FR method, surpassed the critical value of (109 s−1) for all samples. However, with the KAS and FWO methods, these values fell below (109 s−1) within the conversion range of 0.05–0.25. Thermodynamic parameters confirmed the endothermicity of the thermal degradation process.

Co-pyrolysis of municipal sludge and papermaking sludge: Pyrolysis behaviors and heavy metals immobilizations

The co-pyrolysis of municipal sludge (MS) and papermaking sludge (PS) is beneficial for improving the quality of co-pyrolysis biochar and the stability of heavy metals in it. This study investigated the synergistic effect of co-pyrolysis of MS and PS, as well as the influence of different mass ratios (1:9, 3:7, 5:5, 7:3, and 9:1; MS:PS) and pyrolysis temperatures (400–600 ℃) on the physicochemical properties of pyrolysis char, chemical speciation of heavy metals, and their potential ecological risk index. Furthermore, thermodynamic equilibrium calculations were used to study the transformation and stabilization mechanisms of heavy metals during co-pyrolysis. The results indicated that the addition of PS increased the comprehensive pyrolysis index of MS (by 2.09–16.72 times) and the specific surface area of co-pyrolysis char. The inclusion of MS effectively promoted the transformation of heavy metals from unstable fractions to stable fraction, significantly reducing the potential ecological risk index of pyrolysis biochar (by 21.93–41.58 %). The combination of thermodynamic equilibrium calculations and experimental data demonstrated that heavy metals in sludge could be stabilized through the formation of stable heavy metal compounds or their encapsulation within the lattice of inorganic components during co-pyrolysis. These findings suggest that co-pyrolysis of MS and PS is a feasible and promising approach for producing high-quality pyrolysis char with low risk of heavy metals.

Biomass fast pyrolysis kinetics using curie-point pyrolysis: Comparison with pyroprobe and thermogravimetric analysis

In this study, the kinetics of fast pyrolysis of pine wood biomass at short timescales is evaluated using analytical Curie-point and Pyroprobe® pyrolyzers. Curie-point pyrolysis was highly effective in ensuring that the biomass was heated to the set temperatures at very high heating rates and precise time scales. This is the first time the mass loss data of lignocellulosic biomass using a Curie-point pyrolyzer is being reported at short timescales of the order of 10−1 s. COMSOL Multiphysics® simulations, employed to determine the time required for the sample to heat-up to the final reaction temperature, proved that it was 0.2 s in the Curie-point pyrolyzer and 6–8 s in the Pyroprobe® reactor. Within a time period of 0.5 s for temperatures greater than 400 °C, complete conversion of the biomass was achieved using a Curie-point pyrolyzer. The conventional reaction kinetic models were not able to explain the pyrolysis behavior of the sample in a Curie-point pyrolyzer, especially at short timescales of 0–0.5 s. However, the kinetics until 0.4 s, corresponding to the release of light volatiles, is shown to follow the sigmoidal Avrami model, while the major devolatilization stage in the range of 0.4–0.5 s could not be described by a standard kinetic model. This showed that the reactions at short time scales are highly complex processes governed by the competing decomposition rates of the biomolecules. The isothermal mass loss experiments using the Pyroprobe® showed that pyrolysis followed first-order kinetics, and the rate of decomposition was slower as it took 10–20 s for the conversion to attain a steady value. The kinetic compensation for the pyrolysis of pinewood was constructed using the fast pyrolysis data and the kinetics of slow pyrolysis using isoconversional models, and it was found to be ln(A) = 0.18*Ea – 3.12.

Insights into pyrolysis product characteristics and carbon structure evolution of bituminous coal under high-temperature thermal shock

The current investigation aims to reveal the pyrolysis characteristics and particle microstructure evolution of bituminous coal under the high-temperature thermal shock. In the experimental temperatures, the purification of carbon matrix in the coal char is a successive process linear on temperature. In contrast, the graphitization process of carbon structure existed a transition temperature (1600 ℃). Specifically, the range of 1000–1500 ℃ is critical for the transformation of amorphous carbon to disordered graphite, but the growth of graphite microcrystals was minimally affected. While the range of 1600–1900 ℃ is critical for the formation of the graphite-like carbon structure. It is characterized by the release of defective structures such as oxygen-containing functional groups, and a significant increase in crystal size. Although beneficial for the subsequent study of carbon materials, the ordered graphite transformation led to the deactivation of char. The pyrolysis behavior study under thermal shock insight into the thermal behavior of coal char in high-temperature furnaces, as well as a new idea for the clean utilization of coal resources.